U.S. patent number 11,174,740 [Application Number 16/667,150] was granted by the patent office on 2021-11-16 for vane comprising a structure made of composite material and a metal stiffening part.
This patent grant is currently assigned to SAFRAN AIRCRAFT ENGINES. The grantee listed for this patent is SAFRAN AIRCRAFT ENGINES. Invention is credited to Anthony Binder, Vivien Mickael Courtier, Christophe Paul Jacquemard.
United States Patent |
11,174,740 |
Courtier , et al. |
November 16, 2021 |
Vane comprising a structure made of composite material and a metal
stiffening part
Abstract
The invention relates to a vane (7) comprising: a structure made
of composite material, a vane (7) root (16) attachment (9)
comprising a base having a radial outer face (20) and in which a
slot (24) configured to receive the vane (7) root (16) is formed
and two platforms (26), extending on either side of the blade (18)
opposite the radial outer face (20), and two stiffening parts (30),
added and fixed on the radial outer face (20) on either side of the
stilt (17) so as to tightly abut against the stilt (17).
Inventors: |
Courtier; Vivien Mickael
(Moissy-Cramayel, FR), Binder; Anthony
(Moissy-Cramayel, FR), Jacquemard; Christophe Paul
(Moissy-Cramayel, FR) |
Applicant: |
Name |
City |
State |
Country |
Type |
SAFRAN AIRCRAFT ENGINES |
Paris |
N/A |
FR |
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Assignee: |
SAFRAN AIRCRAFT ENGINES (Paris,
FR)
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Family
ID: |
1000005935297 |
Appl.
No.: |
16/667,150 |
Filed: |
October 29, 2019 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20200182073 A1 |
Jun 11, 2020 |
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Foreign Application Priority Data
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Oct 30, 2018 [FR] |
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1860061 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01D
5/282 (20130101); F01D 5/3015 (20130101); F05D
2220/323 (20130101); F05D 2240/80 (20130101); F01D
17/162 (20130101); F05D 2260/30 (20130101); F05D
2300/603 (20130101); F05D 2260/74 (20130101) |
Current International
Class: |
F01D
5/30 (20060101); F01D 5/28 (20060101); F01D
17/16 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 972 757 |
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Jul 2012 |
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EP |
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0 764 765 |
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Mar 1997 |
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ER |
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Other References
Communication dated May 22, 2019 from French National Institute of
Industrial Property in Application No. 1860061. cited by
applicant.
|
Primary Examiner: Verdier; Christopher
Assistant Examiner: Lange; Eric A
Attorney, Agent or Firm: Sughrue Mion, PLLC
Claims
The invention claimed is:
1. A vane of a turbomachine, the vane comprising: a structure made
of composite material comprising a fiber reinforcement obtained by
three-dimensional weaving and a matrix into which the fiber
reinforcement is embedded, the composite material structure
comprising an airfoil blade, a vane root and a stilt extending
between the blade and vane root, a vane root attachment, comprising
a base having a radial outer face and in which a slot configured to
receive the vane root is formed two platforms, extending on either
side of the blade opposite the radial outer face, and two
stiffening parts, added and fixed on the radial outer face on
either side of the stilt so as to abut against the stilt, wherein
the vane has a reduced thickness in the areas in contact with the
stiffening parts so that a thickness of the vane at a free end of
said stiffening parts is continuous.
2. The vane according to claim 1, wherein the stiffening parts
further abut against a portion of the blade.
3. The vane according to claim 1, wherein the stiffening parts are
made of at least one of the following materials: a steel-based
alloy, a titanium-based alloy, a composite material comprising a
fiber reinforcement densified by a matrix.
4. The vane according to claim 3, wherein each stiffening part has
a thickness comprised between 4 mm and 6 mm when the stiffening
parts are made of titanium-based alloy or of composite material and
between 2 mm and 3 mm when the stiffening parts are made of
steel-based alloy.
5. The vane according to claim 1, wherein a recess is formed in the
radial outer face of the attachment on either side of the stilt so
as to form two shoulders, and wherein each shoulder is configured
to receive one of the stiffening parts, a depth of the shoulder
being equal to a thickness of the associated stiffening part at the
radial outer face.
6. The vane according to claim 1, wherein each stiffening part
further extends between one of the platforms and the stilt, a
gasket being positionable between the stiffening part and the
associated platform.
7. The vane according to claim 1 wherein each stiffening part is
monolithic with one of the platforms.
8. The vane according to claim 1, further comprising a series of
screws added and fixed in associated orifices formed in each
stiffening part and in the radial outer face of the attachment.
9. The vane according to claim 1 further comprising a damping
gasket positioned between a free edge of each stiffening part and
the vane.
10. The vane according to claim 1 having a leading edge and a
trailing edge and wherein a radial portion of each stiffening part
has a thinned edge at least at one among the leading edge and the
trailing edge.
11. A vane of a turbomachine comprising: a structure made of
composite material comprising a fiber reinforcement obtained by
three-dimensional weaving and a matrix into which the fiber
reinforcement is embedded, the composite material structure
comprising an airfoil blade, a vane root and a stilt extending
between the blade and the vane root, a vane root attachment,
comprising a base having a radial outer face and in which a slot
configured to receive the vane root is formed and two platforms,
extending on either side of the blade opposite the radial outer
face, and two stiffening parts, added and fixed on the radial outer
face on either side of the stilt so as to abut against the stilt
and against a portion of the blade, wherein a height h of a radial
portion of each stiffening part is comprised between 5% and 25% of
a height of the vane.
12. The vane according to claim 11, wherein the height h of the
radial portion of each stiffening part is comprised between 8% and
15% of the height of the vane.
13. The vane according to claim 11, wherein the height h of the
radial portion of each stiffening part is equal to 10% of the
height of the vane.
14. A vane of a turbomachine, the vane comprising: a structure made
of composite material comprising a fiber reinforcement obtained by
three-dimensional weaving and a matrix into which the fiber
reinforcement is embedded, the composite material structure
comprising an airfoil blade, a vane root and a stilt extending
between the blade and the vane root, a vane root attachment,
comprising a base having a radial outer face and in which a slot
configured to receive the vane root is formed and two platforms,
extending on either side of the blade opposite the radial outer
face, and two stiffening parts, added and fixed on the radial outer
face on either side of the stilt so as to abut against the stilt
and against a portion of the blade, wherein the vane has a reduced
thickness in areas in contact with the stiffening parts so that a
thickness of the vane at a free end of said stiffening parts is
continuous.
15. A vane of a turbomachine comprising: a structure made of
composite material comprising a fiber reinforcement obtained by
three-dimensional weaving and a matrix into which the fiber
reinforcement is embedded, the composite material structure
comprising an airfoil blade, a vane root and a stilt extending
between the blade and the vane root, a vane root attachment,
comprising a base having a radial outer face and in which a slot
configured to receive the vane root is formed, and two platforms,
extending on either side of the blade opposite the radial outer
face, two stiffening parts, added and fixed on the radial outer
face on either side of the stilt so as to abut against the stilt,
and at least one metal structural shield added and fixed on a
leading edge of the vane and/or on a trailing edge of the vane, the
stiffening parts therefore extending beyond the platforms and being
positioned on a portion of the blade so as to be aligned with said
structural shield, wherein the stiffening parts and the at least
one structural shield extend end-to-end, without overlapping.
16. The vane according to claim 15, wherein the at least one
structural shield and the stiffening parts cover an entire portion
of the blade between the leading edge and the trailing edge so that
a surface of said portion of the blade does not have a
discontinuity likely to disturb the flow.
Description
FIELD OF THE INVENTION
The invention relates to a vane comprising a structure made of
composite material.
The invention relates more particularly, but not exclusively, to a
vane intended to be used in an unducted fan rotor of an aircraft
engine (such as an "Open Rotor"-type engine having two rotating
propellers or an USF "Unducted Single Fan"-type engine having a
movable vane assembly and a stationary vane assembly or a turboprop
having a single-propeller architecture) or in a wind turbine
rotor.
TECHNOLOGICAL BACKGROUND
The advantage of the unducted fan engines is that the diameter of
the fan is not limited by the presence of a fairing, so that it is
possible to design an engine having a high bypass ratio, and
consequently a reduced fuel consumption.
Thus, in this type of engine, the vanes of the fan can have a large
span.
In addition, these engines generally comprise a mechanism that
allows changing the pitch angle of the vanes in order to adapt the
thrust generated by the fan according to the different phases of
flight.
However, the design of such vanes requires taking into account
conflicting constraints.
On the one hand, the dimensioning of these vanes must allow optimal
aerodynamic performances (maximizing efficiency and providing
thrust while minimizing losses). Improved aerodynamic performances
of the fan tend to an increased bypass ratio (BPR), which results
in an increased outer diameter and therefore an increased span of
these vanes.
On the other hand, it is also necessary to guarantee a resistance
to the mechanical stresses that may be exerted on these vanes while
limiting their acoustic signature.
Furthermore, on the unducted fan architectures, the engine is
generally started with a very open pitch. Indeed, a very open pitch
enables consumption of the power by the torque, which ensures the
safety of the machine while guaranteeing low fan speeds.
However, with a very open pitch, the vanes undergo a turbulent
aerodynamic flow, that is completely separated, which generates a
broadband vibrational excitation. Especially on wide-chord vanes
with large span, the bending force is intense although the engine
speed is not maximum.
In normal operation, during the ground and flight phases, the pitch
is changed (the pitch angle is more closed). The aerodynamic flow
is therefore perfectly non-turbulent (re-adhered to the aerodynamic
profile). The broadband loads disappear, the rotational speed is
higher, and the bending force is controlled.
Currently, these vanes are generally made of metal material. If the
metal material vanes have good mechanical strength, they have the
disadvantage of having a relatively significant mass.
In order to reduce this mass, it is desirable to be able to
manufacture these composite material vanes. However, the intense
aerodynamic forces to which these vanes would be subjected could
damage the vane and/or the hub in the interface area between these
vanes and the hub of the fan rotor. This problem arises more
particularly when the vanes are connected to the hub by means of
broached attachments.
SUMMARY OF THE INVENTION
An object of the invention is therefore to propose a vane
comprising a structure made of composite material, adapted to be
used with a variable-pitch mechanism, while being capable of
withstanding intense aerodynamic forces.
For this purpose, the invention proposes a vane, in particular a
vane of a rotor of a turbomachine, comprising: a structure made of
composite material comprising a fiber reinforcement obtained by
three-dimensional weaving and a matrix into which the fiber
reinforcement is embedded, the composite material structure
comprising an airfoil blade, a vane root and a stilt extending
between the blade and the vane root, a vane root attachment,
comprising a base having a radial outer face and in which a slot
configured to receive the vane root is formed two platforms,
extending on either side of the blade opposite the radial outer
face and two stiffening parts, added and fixed on the radial outer
face on either side of the stilt so as to tightly abut against the
stilt.
Some preferred but non-limiting characteristics of the vane
described above are the following, taken individually or in
combination: the stiffening parts further abut against a portion of
the blade. the stiffening parts are made of at least one of the
following materials: a steel-based alloy, a titanium-based alloy, a
composite material comprising a fiber reinforcement densified by a
matrix. each stiffening part has a thickness comprised between 4 mm
and 6 mm when the stiffening parts are made of titanium-based alloy
or of composite material and between 2 mm and 3 mm when the
stiffening parts are made of steel-based alloy. a recess is formed
in the radial outer face of the attachment on either side of the
stilt so as to form two shoulders, and in which each shoulder is
configured to receive one of the stiffening parts, a depth of the
shoulder being substantially equal to a thickness of the associated
stiffening part at the radial outer face. each stiffening part
further extends between one of the platforms and the stilt, a
gasket being able to be positioned between the stiffening part and
the associated platform, where each stiffening part is monolithic
with one of the platforms. the vane further comprises a series of
screws added and fixed in associated orifices formed in each
stiffening part and in the radial outer face of the attachment. the
vane has a reduced thickness in the areas in contact with the
stiffening parts so that a thickness of the vane at the free end of
said stiffening parts is substantially continuous. the vane further
comprises a damping gasket, positioned between a free edge of each
stiffening part and the vane. the vane has a leading edge and a
trailing edge and a radial portion of each stiffening part has a
thinned edge at the leading edge and/or at the trailing edge.
BRIEF DESCRIPTION OF THE DRAWINGS
Other characteristics, objects and advantages of the present
invention will become more apparent upon reading the following
detailed description, and in relation to the appended drawings
given by way of non-limiting examples and in which:
FIG. 1 schematically represents one example of an engine including
an unducted fan.
FIG. 2 schematically represents a fan vane and an actuating
mechanism that allows changing the pitch angle of the vanes of the
fan.
FIG. 3 is a schematic partial sectional view of one example of a
vane according to one embodiment of the invention.
FIG. 4 is a perspective view of one exemplary embodiment of a
stiffening part that can be used in a vane according to the
invention.
FIG. 5 is a schematic partial sectional side view of one example of
a vane fixed in an associated attachment.
DETAILED DESCRIPTION OF ONE EMBODIMENT
In FIG. 1, the engine 1 represented is an "Open Rotor"-type engine,
in a configuration commonly referred to as "pusher" (i.e. the fan
is placed at the rear of the power generator with an air inlet
located on the side, to the right in FIG. 1).
The engine comprises a nacelle 2 intended to be fixed to a fuselage
of an aircraft, and an unducted fan 3. The fan 3 comprises two
counter-rotating fan rotors 4 and 5. In other words, when the
engine 1 is in operation, the rotors 4 and 5 are driven in rotation
relative to the nacelle 2 about the same axis of rotation X (which
coincides with a main axis of the engine), in opposite
directions.
In the example illustrated in FIG. 1, the engine is an "Open
Rotor"-type engine, in "pusher" configuration, with
counter-rotating fan rotors. However, the invention is not limited
to this configuration. The invention also applies to "Open
Rotor"-type engines, in "puller" configuration (i.e. the fan is
placed upstream of the power generator with an air inlet located
before, between or just behind the two fan rotors).
In addition, the invention also applies to engines having different
architectures, such as an architecture comprising a fan rotor
comprising movable vanes and a fan stator comprising stationary
vanes, or a single fan rotor.
The invention is applicable to turboprop-type architectures
(comprising a single fan rotor).
In FIG. 1, each fan rotor 4, 5 comprises a hub 6 rotatably mounted
relative to the nacelle 2 and a plurality of vanes 7 fixed to the
hub 6. The vanes 7 extend substantially radially relative to the
axis rotation X of the hub.
In the present application, the upstream and the downstream are
defined relative to the direction of normal flow of the gas in the
rotor 4, 5 and through the turbomachine. Moreover, the axis X of
the rotor 4, 5 is its axis of rotation. The axial direction
corresponds to the direction of the axis X and a radial direction
is a direction perpendicular to this axis and passing therethrough.
Moreover, the circumferential direction corresponds to a direction
perpendicular to the axis X and not passing therethrough. Unless
otherwise specified, the terms "inner" and "outer", respectively,
are used with reference to a radial direction so that the inner
portion or face of an element is closer to the axis X than the
outer portion or face of the same element.
As illustrated in FIG. 2, the fan 3 further comprises an actuating
mechanism 8 for collectively changing the pitch angle of the vanes
of the rotors, in order to adapt the performances of the engine to
the different phases of flight. For this purpose, each vane 7
comprises an attachment part 9 disposed at the vane root. The
attachment part 9 is rotatably mounted relative to the hub 6 about
a pitch axis Y. More specifically, the attachment part 9 is
rotatably mounted inside a housing 10 arranged in the hub 6, by
means of balls 11 or other rolling elements.
The actuating mechanism 8 comprises an actuator 12 comprising a
body 13 fixed to the hub 6 and a rod 14 adapted to be driven in
translation relative to the body 12. The actuating mechanism 8
further comprises an annular slide 15 mounted secured to the rod 14
and a pin 16 mounted secured to the attachment part 9. The pin 16
is adapted to slide in the slide 15 and to rotate relative to the
slide 15, so as to convert a translational movement of the rod 14
into a rotational movement of the attachment part 9, and
consequently a rotational movement of the vane 7 relative to the
hub 6 about its pitch axis Y.
The vane 7 is a structure made of composite material comprising a
fiber reinforcement obtained by three-dimensional weaving and a
matrix into which the fiber reinforcement is embedded. This
composite material structure comprises a root 16, a stilt 17 and an
airfoil blade 18.
The fiber reinforcement can be formed from a one-piece fiber
preform obtained by three-dimensional or multilayer weaving with
progressive thickness. It can in particular comprise carbon, glass,
aramid and/or ceramic fibers. The matrix for its part is typically
a polymer matrix, for example epoxide, bismaleimide or polyimide or
a carbon matrix. The vane 1 is then formed by molding by means of a
vacuum resin injection process of the RTM ("Resin Transfer
Molding") or VARRTM ("Vacuum Resin Transfer Molding") type.
Each housing 10 receives a pivoting attachment 9 of a vane 7. The
root 16 of the vane 7 is retained in the attachment 9, the stilt 17
and the blade 18 extending out of the hub 6. The attachment 9
comprises, in a manner known per se, a base having a radial outer
face 20 and two symmetrical and inclined opposite flanks 22
delimiting a broaching slot 24 in which the root 16 of the vane 7
is retained. The root 16 is generally wider than the rest of the
blade 18. The flanks 22 are therefore inclined towards each other
and form bearings.
The attachment 9 can be made, conventionally, of steel or
titanium.
Two platforms 26 are further fixed on the attachment 9 on either
side of the blade 18 and cover the slot 24 so as to reconstitute
the stream of the rotor 4, 5. The platforms 26 can be made either
of composite material or of metal.
As indicated above, the root portion 16 of the vane 7 is intended
to allow the attachment of the vane 7 to the attachment 9 and
extends for this purpose between the bottom of the slot 24 and the
outlet of the bearings. The airfoil blade 18 portion is for its
part adapted to be placed in an airflow, when the engine is in
operation, in order to generate a lift. Finally, the stilt 17
corresponds to the area of the blade 18 which extends between the
root 16 and the blade 18 that is to say between the outlet of the
bearings and the platforms 26.
The vane 7 further comprises two stiffening parts 30, added and
fixed on the radial outer face 20 of the attachment 9, on either
side of the stilt 17, so as to tightly abut against the stilt 17
and, optionally, a portion 18a of the blade.
The stiffening parts 30 are metallic, for example in a
titanium-based alloy or a steel-based alloy, or made of a very
stiff composite material, so as to stiffen the root 16 of the vane
7 above the bearings and thus limit the displacements induced by
the bending vibrations of the vane 7. Therefore, they act as a
support taking up the intense forces coming from the aerodynamics
when the flow is separated (for example in the case where the pitch
angle is very open, as at startup). Thus, the stiffening part 30 is
based on a material stiffer than the root 16 of the vane 7 and
stiffer than the attachment 9 which is typically made of titanium.
The stiffening part 30 may be made of titanium-based material but
more preferably of steel-based material (200 GPa characteristic) to
be thinner. Alternatively, the stiffening part 30 may be made of a
composite-based material having a fiber reinforcement densified by
a matrix (characteristic 200 GPa), for example of a laminate-based
material, with the strips of the plies of the laminate being
predominantly in radial orientation (in the direction of the
section). Plies with weaving orientation at 45 degrees with respect
to the radially oriented plies are provided in the laminate as
complements to the radially oriented plies.
For this purpose, each stiffening part 30 comprises a
circumferential portion 32 configured to be in surface abutment
against the radial outer face 20 of the attachment 9 and a radial
portion 34 configured to be in surface abutment against the stilt
17 and, where appropriate, a portion 18a of the blade. The
circumferential portion 32 and the radial portion 34 are monolithic
and connected to each other via a curved junction portion 36.
Preferably, in order to prevent swiveling of the root 16 of the
vane 7, a height h of the radial portion 34 of each stiffening part
30 is comprised between 5% and 25% of the height of the vane 7,
preferably between 8% and 15% of said height, for example in the
order of 10%. By height of the vane 7, it will be understood here
the dimension along an axis radial to the axis of the rotor 4, 5
between the lower limit of the stilt 17 and the radial outer end of
the blade 18 (that is, to say the tip of vane 7).
In addition, the height h of the radial portion 34 can be adapted
to modify the frequency placement of some frequency modes of the
vane 7, which further allows avoiding possible frequency crossings
over the range of use of the rotor 4, 5.
The curvature of the joining portion 36 is for its part dimensioned
so as to optimally take up the forces coming from the vane 7 and to
transmit them to the circumferential portion 32.
Where appropriate, as shown in FIGS. 4 and 5, an axial width L of
the circumferential portion 32 may be greater than an axial width 1
of the radial portion 34. In other words, the circumferential
portion 32 may not expand over the entire chord of the vane 7.
Each stiffening part 30 further has an inner face 38, which extends
opposite the radial outer face 20 and the stilt 17, and an outer
face 39 which is opposite to the inner face 38, as well as a
thickness e which corresponds to the minimum distance between the
inner face 38 and the outer face 39 in the circumferential portion
32.
The thickness e of each stiffening part 30 is comprised between 4
mm and 6 mm when it is made of titanium-based alloy or of composite
material and between 2 mm and 3 mm when it is made of steel-based
alloy.
In order to assemble the fan rotor 4, 5, for each attachment 9 and
each vane 7, a shim 19 may, in a conventional manner, be mounted in
the bottom of the slot 24. The root 16 of the vane 7 may then, be
inserted over the shim 19. Then, the stiffening parts 30 are added
on the attachment 9 by inserting them radially on either side of
the vane 7 and fixed in this position. For this purpose, a first
and a second series of orifices 37 are respectively formed in the
circumferential portion 32 of the stiffening parts 30 and in the
radial outer face 20, on either side of the slot 24, each second
orifice 37 extending opposite a first orifice, and a series of
screws are added and fixed in each first and second orifice 37 so
as to block the stiffening parts 30 relative to the attachment 9.
Preferably, bushings, configured to cooperate with the screws, are
further provided in the second orifices 37. The screws thus allow
ensuring the resistance of the vane 7 to centrifugal forces.
It will be noted that the position of the second orifices 37
relative to the slot 24, and therefore to the vane 7, is chosen so
that the radial portion 34 of the stiffening parts 30 is tightly
mounted against the stilt 17 (and, where appropriate, a portion of
the blade 18) over its entire inner face 38. In other words, the
radial portions 32 exert a force on the vane 7 when stopped and
during all phases of flight. It is this tight surface contact that
allows stiffening the vane 7 by adding additional abutment points
at a distance from the attachment 9. The stiffening parts 30 are
therefore not adhered to the vane 7, thus allowing small relative
movements between said stiffening parts 30 and the vane 7 in
operation.
The platforms 26 are then added and fixed on the attachment 9 or
the hub in a conventional manner. As can be seen in FIG. 3, in one
embodiment, the radial portion 34 of each stiffening part 30
extends between one of the platforms 26 and the stilt 17. A gasket
28 can then be positioned between the stiffening part 30 and the
associated platform 26 so as to ensure continuous contact between
the platform 26 and the stiffening parts 30 and thus limit the
risks of air leaks from the stream toward the hub and therefore the
aerodynamic losses. The gasket 28 may for example be fixed on the
ridge of the platforms 26 which abuts against the stilt 17.
Alternatively, each platform 26 may be monolithic with one of the
stiffening parts 30. The platforms 26 are then formed integrally
and in one piece with the associated stiffening part 30, or added
and fixed thereon. In this variant, the platforms 26 are therefore
fixed on the attachment 9 with the stiffening parts 30.
Where appropriate, two recesses 21, each configured to accommodate
the circumferential portion 32 of one of the stiffening parts 30,
may be formed in the radial outer face 20 of the attachment 9, on
either side of the stilt 17. These recesses 21 thus form shoulders
that open into the slot 24 and allow taking up the forces coming
from the vane 7.
The recesses 21 may be obtained by machining the radial outer face
20 of the attachment 9, or alternatively during the molding of the
attachment 9.
Optionally, a depth (which corresponds here to the dimension along
an axis normal to the radial outer face 20) of the shoulder is
substantially equal to the thickness e of the circumferential
portion 32 of the stiffening part 30 at the shoulder, so as to
reconstitute a smooth surface at the radial outer face 20.
Where appropriate, a damping gasket 29 may be positioned between a
free edge of each stiffening part 30 and the vane 7 in order to
ensure continuous contact between the stiffening part 30 and the
vane 7 despite possible small deformations and thus limit the
appearance of clearances. This damping gasket 29 thus allows
limiting the aerodynamic losses likely to reduce the efficiency of
the rotor 4, 5.
For example, the damping gasket 29 can be added and fixed in a
groove formed in the inner face 38 of each stiffening part 30.
The damping gasket 29 may for example be fixed on the radial outer
edge 30c, on the upstream edge 30a and on the downstream edge 30b
of the radial portion 34 of each stiffening part 30.
In one embodiment, when the stiffening parts 30 partially cover the
blade 18, which extends into the gas flow in operation, the vane 7
has a reduced thickness in the portion 18a of the vane which is in
contact with the stiffening parts 30 and at the stilt 17, so that a
thickness of the vane 7 at the free end of said stiffening parts 30
is substantially continuous. In other words, the thickness of this
portion 18a of the blade and of the stilt 17 is reduced so that,
when the stiffening parts 30 are added and fixed on the vane 7, the
latter has a continuous aerodynamic surface, that is to say devoid
of protruding ridge, so as not to generate aerodynamic losses
likely to reduce the efficiency of the rotor 4, 5.
For this purpose, the composite material structure may be joggled
at the interface between the vane 7 and the stiffening parts 30.
For example, during the weaving of the fiber preform, the weft
strands can be chosen so that those forming the stilt 17 and the
portion 18a of the blade have a smaller diameter than those forming
the rest 18b of the blade 18. The number of warp strands may not be
modified compared to a conventional vane 7.
Alternatively, additional warp strands may be introduced during
weaving of the fiber preform in the areas 18b of the blade 18 which
are not intended to be covered by the stiffening parts 30. This
embodiment slightly increases the thickness of the vane 7 at its
aerodynamic surface, compared to the first variant which allows
maintaining its nominal thickness. Warp strands are added but for
their maintenance, these weft strands are also added.
According to yet another variant, the composite material structure
can be both joggled and additional warp and weft strands can be
introduced during weaving of the fiber preform.
Thus, for these two variants, strands are woven, including areas
with free weaving spaces, leaving weaving-"float" areas. Non-woven
(or loosely woven) spaces are located between tightly woven
spaces.
The added warp strands will allow getting thickness and the weft
strands will ensure the maintenance. In addition, thickness
variations are possible without weaving pattern variation, only by
the action of changing the spacing between the strands.
It will be noted that, in the case where the stiffening parts 30
are made of a material whose stiffness is in the order of that of
the composite material of the vane 7 (in the direction of the warp
yarns of the fiber preform), for example when they are in a
titanium alloy or in a composite material, the root 16 cutouts are
slightly refined, which makes it possible to guarantee a gain in
stiffness since the stiffening parts 30 cover the lower portion of
the vane 7.
In the case where the stiffening parts 30 are in a material whose
stiffness is greater than that of the composite material of the
vane 7 (in the direction of the warp yarns of the fiber preform),
for example when they are in a steel-based alloy, the root 16
cutouts can be refined while increasing the stiffness of the vane
7, which is beneficial for the efficiency of the rotor 4, 5.
When necessary, the vane 7 may further comprise a metal structural
shield 40 added and fixed on the leading edge and/or on the
trailing edge of the vane 7. By leading edge, it will be understood
here the edge of the vane 7 configured to extend opposite the flow
of the gases entering the rotor 4, 5. It corresponds to the
anterior portion of the aerodynamic profile which faces the air
stream and which divides the air flow into an intrados flow and an
extrados flow. The trailing edge for its part corresponds to the
posterior portion of the aerodynamic profile, where the intrados
and extrados flows meet.
When the stiffening parts 30 cover a portion 18a of the blade (and
therefore extend beyond the platforms 26, in the stream), said
parts are positioned on the blade 18 so as to extend in the
extension of said structural shield 40, without overlapping. The
structural shield(s) 40 and the stiffening parts 30 are further
disposed end-to-end so that the portion 18a of the blade is covered
either by the structural shield 40 or by a stiffening part 30,
between its leading edge and its trailing edge, so that the surface
of the vane 7 does not have a discontinuity likely to disturb the
flow.
Alternatively, when the vane 7 is devoid of structural shield, the
upstream edge 30a and the downstream edge 30b of the stiffening
part, which cover the intrados (or the extrados) of each stiffening
part 30 at the leading edge and trailing edge of the vane 7 are
thinned. The thinning is for example carried out by joggling in the
direction of the weft strands of the fiber preform, in the area
intended to form these edges 30a, 30b.
* * * * *